Electrostatic discharging system

ABSTRACT

The electrostatic environment inside an oil carrier tank is measured through a sensor which produces an alternating current output signal which is fed separately to two power units, one of which produces a signal if the polarity of the field sensed is positive and the other of which produces a signal if the polarity of the field sensed is negative, each circuit amplifying its specific signal to a predetermined level. The parallel circuits are connected to a high voltage circuit which produces an electrostatic field having a predetermined polarity and a magnitude which is proportional to the electrostatic field sensed. The generated electrostatic field is applied to an ionizer nozzle through which water is sprayed into the tank. The water is electrostatically charged by the nozzle to have a polarity opposite to the polarity sensed by the sensor and effectively neutralizes the electrostatic charge within the tank.

De La Cierva [11] 3,821,603 June 28, 1 974 ELECTROSTATIC DISCHARGINGSYSTEM [76] Inventor: Juan J. De La Cierva, Apolonio Morales 21, Madrid,Spain [22] Filed: Feb. 20, 1973 [21] Appl. No.: 333,656

Related US. Application Data [63] Continuation of Ser. No. 239,567,March 30, 1972,

Primary Examiner-J. D. Miller Assistant Examinerl-larry E. Moose, Jr.Attorney, Agent or Firm-Lewis H. Eslinger 571 A ABSTRACT Theelectrostatic environment inside an oil carrier tank is measured througha sensor which produces an alternating current output signal which isfed separately to two power units, one of which produces a signal if thepolarity of the field sensed is positive and the other of which producesa signal if the polarity of the field sensed is negative, each circuitamplifying its specific signal to a predetermined level. The parallelcircuits are connected to a high voltage circuit which produces anelectrostatic field having a predetermined polarity and a magnitudewhich is proportional to the electrostatic field sensed. The generatedelectrostatic field is applied to an ionizer nozzle through which wateris sprayed into the tank. The water is electrostatically charged by thenozzle to have a polarity opposite to the polarity sensed by the sensorand effectively neutralizes the electrostatic charge within the tank.

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SHEET 0F 8 SEA/501? cow 7%?04 AND A; ARM u/v/T' 1 ELECTROSTATICDISCHARGING SYSTEM This is a continuation of application Ser. No.239,567, filed Mar. 30, 1972, now abandoned.

I BACKGROUND OF THE INVENTION The invention relates to an electrostaticdischarging system for use in tanks which contain liquid fuel, and moreparticularly to a system for neutralizing theelectrostatic charge in thetanks of oil carriers. The'system disclosed herein is related in somerespects to the discharging systems described in US. Pat. Nos. 3,260,893and 3,427,504 of which the present application is a joint inventor.

It is necessary in the transportation and storage of liquid fuelproducts to ensure that no electrostatic discharges take place in theform of sparks in an explosive atmosphere. This is particularly truewith regard to the tanks of oil carriers. In such oil carriers thestorage departments are generally divided into several tanks by means oflarge bulkheads. On the return trip, after the tanks are emptied, theship must carry a minimum of load in order to be able to sail so theremoved oil is replaced by a salt water ballast stored in the same'tank.

At the shipping port, before being refilled with oil, the oil carrierstanks are washed.

In practice the tanks'are washed with water blasts under high pressure.The blasts of water are atomized and generally beat against thebulkheads. In so doing the water acquires an electrostatic charge andalso introduces an electrostatic space chargeto the tank. Theelastrostatic charge is generated as a consequence of the differentfunctions of the atoms placed at the water breakup surfaces when thebreaking particles are not homogeneous in saltiness, impurities,temperature and other factors.

The nature of this electrostatic charging process is such that it isalmost impossible to predict its intensity or polarity. For example whentanks are washed with pure sea water they sometimes have a positivecharge while when the same tanks are washed with fresh water the tanksmay have a resultant negative charge. When the magnitude of theresulting electrostatic field within the tank surpasses the airsdielectrical strength, an electric are results which is capable ofcausing an explosion of the mixture of hydrocarbon gases and air oftenfound in such tanks. At the present time'the only practical method toprevent such explosions is to control concentration of the gaseousmixture within the tank. This is a complicated and time consumingprocess which interferes with the washing cycle.

SUMMARY OF THE INVENTION The foregoing problems are overcome by thepresent invention of an automatic electrostatic discharging system foruse in a liquid fuel container comprising means for sensing themagnitude and polarity of an electrostatic field within the containerand for producing a first output signal representative of the magnitudeand polarity of the electrostatic field sensed. A first circuitresponsive to the first output signal produces a second output signalwhenthe polarity of the field sensed is positive and a second circuitresponsive to the first output signal produces a third output signalwhen the polarity of the field sensed is negative. A third circuitresponsive to the second and the third output signals produces a highvoltage, electrostatic potential proportional in magnitude to theelectrostatic field sensed by the sensor and having a predeterminedpolarity. This high voltage, electrostatic potential is applied to waterparticles sprayed into the container to electrostatically charge thewater particles with a polarity opposite to that sensed by the sensingmeans.

In a preferred embodiment the means for electrostat ically charging thespray of water includes an ionizer nozzle which is cone shaped and whichforms a cone shaped spray of water. An insulated electrode in theinterior surface of the cone provides an electrostatic field whichinduces a surface charge on the atomized water particles through thedielectric insulation surrounding the electrode.

In one embodiment the sensing means includes a device mounted inside thetank having two vanes which are coaxial and which rotate in oppositedirections. The

vanes each have four, forty five degree segments. A

first one of the vanes is grounded and continuously exposed to the fieldwithin the container. The second vane is periodically exposed to theelectrostatic charge in the atmosphere surrounding the sensor by thefirst vane as the two vanes are counterroated, thereby causing analternating signal to be produced in the second vane. This alternatingsignal is representative in polarity and magnitude of the electrostaticfield sensed. In one preferred embodiment the phase of the signal, whencompared with a reference signal generated in synchronism with thecounterrotation of the vanes, is the indication of the polarity -of theelectrostatic field sensed.

It is therefore an object of the present invention to I provide a systemfor sensing the polarity and magnitude of an electrostatic charge withina petroleum tank and for neutralizing that charge by spraying in waterparticles which are electrostatically charged to the same magnitude butwith a polarity opposite to that of the field within the tank.

It is still another object of the invention to provide a simplifiedwater ionizing nozzle for use in discharging the electrostatic chargewithin a petroleum tank.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of certain preferred embodiments of theinvention, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of adischarging apparatus according to one simplified embodiment of theinventron;

FIG. 2 is a partiallyschematic, longitudinal sectional view of anatomizing nozzle according to one embodiment of the invention;

FIG. 2A is a partially schematic, longitudinal sectional view of amodified nozzle according to another embodiment of theinvention;

FIG. 3 is a graph illustrating the charging and dis charging rates foran electrostatic field obtained in a laboratory test of one embodimentof the invention;

FIG. 4 is a graph illustrating the charging rate of an electrostaticfield obtained in a test of one embodiment ofv the invention in an oilcarrier tank; I

FIG. 5 is a graph illustrating the discharging rate of an electrostaticfield in the oil carrier tank referred to in FIG. 4 using the sameembodiment of the invention;

FIG. 6 is a schematic diagram of a test arrangement of the inventionillustrating the fundamental principles of the invention;

FIG. 7 is a schematic diagram of an installation of one preferredembodiment of the invention aboard an oil carrier vessel;

FIG. 8 is a system diagram illustrating the structure of a portion ofthe embodiment of FIG. 7; and

FIG. 9 is a block diagram of the electronic sensing system of theembodiment depicted in FIGS. 7 and 8.

DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS Referring now moreparticularly to FIG. 1 the fundamental aspects of a simplifiedembodiment of the invention will be described. An electrostatic fieldsensor 1 which is mounted in an oil carrier tank 10 has three outputterminals designated A, B and C. At the terminal A the sensor produces avoltage proportional to the electrostatic field which is measured andthis signal is fed to a unity of measurement and control circuit 2. Thesignal is further registered graphically on a recording voltmeter (eg. achart recorder) 3.

Besides the signal observed at terminal A the. sensor 1 also suppliesalternating signals modulated at a fre-- quency of 1.7 Kl-Iz. These twosignals are produced at terminals B and C and are fed to two power units4 and 5, respectively. As will be explained in greater detail further inthe specification the sensor includes inner and outer coaxial vanes 11which counterrotate with respect to each other. The inner vane isalternately exposed to and then shielded from the electrostatic field inthe tank 10 by the outer vane. Each time the outer vane overlies theinner vane the vanes are said to intercept each other. Hence the vanesact as a chopper to convert the tank space'charge into a current whichis used to modulate the 1.7 KHz alternating signal. The sensor 1 issimilar in its construction to the sensor disclosed in US. Pat. No.3,427,504 referred to above.

The power unit 4 demodulates the alternating signal from the terminal Band produces an output signal when the charge sensed by the sensor 1 ispositive in polarity. Similarly the power unit 5 demodulates thealternating signal from the terminal C and produces an output signalwhen the electrostatic field sensed is negative. The output signals fromthe power units 4 and 5 are fed to rectifying circuits 6 and 7,respectively. The rectifying circuits 6 and 7 produce high voltagesignals representative of the output from the power units 4 and 5. Thehigh voltage signals from the rectifying circuits 6 and 7 are fed to anoutlet mixer 8 which combines the output signals and converts them intoa single high voltage signal with a magnitude proportional to themagnitude of the electrostatic field measured by the sensor 1 and with apredetermined polarity. As will be explained further in thespecification this predetermined polarity in the preferred embodimentsof the invention is the same as the polarity of the field sensed by thesensor.

A single high voltage output signal from the outlet mixer 8 is.connected to an ionizer nozzle 9. Theionizer nozzle 9 imparts a chargeto the water particles sprayed into the tank through the nozzle from ahigh pressure source 12 which is opposite in polarity to the nozzlecharge to counteract the electrostatic field inside the tank 10.

Referring now more particularly to FIG. 2 the ionizer nozzle 9 has abody portion 900 in the inner space of which there is provided a core901 having a snug fit with the interior of the body portion 900. Thecore 901 has a plurality of helical grooves 908, for example threegrooves as shown in the FIG. 2. The body portion 900 is provided with anopening 902 at its downstream end. The outer portion of the opening 902is encircled by a cone 904 of electrically insulating material, such asa fluorinated hydrocarbon, for example. A cone shaped electrode 903madeof an electrically conductive material is encased within the insulatedcone 904. The electrode 903 is connected at a break 905 in theinsulating material to an electrical conductor 906 which is connected tothe outlet mixer 8.

Water from the source 12 being pressure forced into the upstream end 907of the body 900 of the nozzle 9 has a rotating motion imparted to it bythe helical grooves 908 and, upon being forced through the opening 902,forms a hollow cone of water 909. Since the water flow rate is uniform,but the diameter of the cone increases, the water cone 909 consequentlybreaks up into atomized water particles. This atomization of the watercone takes place within the zone of influence of the metal coneelectrode 903 so that an electrostatic charge is imparted to the waterparticles which are then projected into the tank.

In FIG. 2A a modified form of the nozzle is illustrated having a cone ofinsulating material 909 in which a plurality of interconnected rings 910of electrically conductive material are encased. The rings 910 arecoaxial with the longitudinal axis of the cone and are spaced apart fromeach other. They are each interconnected by high value resistors 911 tothe electrode 912 which is connected to the outlet mixer 8. Theadvantage of the modification is that when there is a local fault in thecone insulation the remainder of the cone is not rendered unusable butonly the ring which is directly affected by the fault. Since very littlecurrent is required to electrostatically charge the water particles, theresistors 911-effectively insulate the ring in which the fault occursfrom the remaining rings.

It is necessary that the electrodes of the nozzles in both of theembodiments of FIGS. 2 and 2A be insulated with a material havingrelatively high insulating properties not only so that a coronadischarge does not take place which might cause an explosion but alsobecause of the process by which water particles are charged. Thisprocess is termed condensive induction. In effect, the electrode of thenozzle acts as one plate of a condensor or capacitor and the water actsas the opposite plate with the insulation surrounding the electrodeacting as the dielectric material. Thus when an electrical potential isapplied to the ionizing electrode the exterior surface of the water incontact with the dielectric, insulating material becomes electrified bya superficial charge having a polarity opposite to that of theelectrode. As the water is atomized, the superficial charge created inthe water is retained in each of the atomized water particles whichcontinue on their way to neutralize the space charge within the tank.

Referring now more particularly to FIG. 3 the results obtained during anexperimental test of the system described above in regard to FIG. 1 areillustrated. A tank was first electrostatically charged by means ofwater ionized through the nozzle 9 to simulate the tank washingprocedure carried out in an oil carrier tank. The tank was thendischarged through the same apparatus as described above. The spacecharge was increased from l volts per meter to +500 volts per meterwhile the nozzle was charged with a voltage of 350 volts per meter. Thebuild up of the charge was accomplished in only slightly more than 75seconds. The space charge was discharged by the apparatus as describedabove in approximately 70 seconds.

Starting from zero electrostatic potential the tank was recharged in 110seconds to approximately +500 volts per meter and was then discharged inthe manner described above in approximately 1 15 seconds. Finally, theprocess was repeated again in the last curve of FIG. 3. At this time theionizer nozzle was placed under a voltage of approximately +150 voltsper meter to produce a negative field in the tank. The tank was thendischarged by the apparatus in approximately 75 seconds.

In FIG. 4 the results of placing the sensor l and the ionizer nozzle 9in the tank of an actual oil carrier are graphically illustrated. Thetank was electrostatically charged by washing it in the usual manneruntil the charge reached the level at which the sensor became saturated.Then the natural discharge of the tank was allowed to reduce thepotential to just under the level of saturation of the sensor. In FIG. 5the discharging affect of the apparatus in the same tank is illustratedand it is clear that from an electrostatic field potential of 900 voltsper meter the system discharged it to 630 volts per meter inapproximately 1 20 seconds. The field was not completely neutralized dueto the hugh dimensions of the tank in relation to the prototype nozzleemployed.

Referring now more particularly to FIG. 6 a test arrangement for theinvention is illustrated wherein a table 13 which is completelyelectrically isolated from the ground by a pair of insulators 14supports a metallic container 15 which is filled with water 16. A sourceof compressed gas 17 is connected to the tank 15 to pressurize thewater. The pressure is regulated by an automatic valve 18 in the line 20connecting the tank of gas 117 to the container 15. The tank 15 isconnected to an ionizing nozzle 19 by a pipe 21 which carries thepressurized water to the nozzle.

The nozzle 19 is connected to a battery powered, high voltage generatingsource 22 mounted on the table 13. The voltage applied to the nozzle 19is measured by a voltmeter 23. The discharge current generated in thenozzle 19 is measured with respect to the ground by a picoamperemeter 24connected between the battery system 22 and the ground.

A preferred embodiment of the invention for actual use in each tank- 100of an oil carrier is illustrated in FIGS. 7, 8 and 9. The tank 100 iscleaned with water supplied by a pipe Pl through a first wash valve V]and a second wash V2 (FIG. 7). Between the wash valves through a pipe P5to the sensor unit generally designated 110. The water supplied from theincremental pressure pump to the pipe P5 is used to help clean any oilresidue from the vanes R02 and 1103.

The pressurized fluid supplied through the line P2 drives the hydraulicturbine 101. The turbine 101 is mechanically linked to a generator oralternator 106, to the driving mechanism 111 of the sensor 110., and toa compressed air pump 104. The compressed air pump 1104 supplies asource of compressed air through the hollow drive shafts of the vanes102 and 1103 which blows between vanes and thus purges them ofcontaminated water. This purging process is done periodically during thewashing cycle to ensure the accuracy of the readings of the sensor H0.

The incremental pressure pump also supplies a high pressure output flowthrough a pipe P6 to an ionizing nozzle 109. The nozzle l09'ispreferably of a construction substantially identical to the constructionof the embodiment depicted in FIG. 2A.

The sensor unit 1110 has two coaxial vanes; vane 102 which is aninternal vane and vane 103 which is an external vane. As indicated bythe directional arrows in FIG. 8, the vanes 1102 and 103 rotate inopposite directions. The vanes in one preferred embodiment of theinvention each comprise four equally spaced octants, thus each vane isin the shape of four 45 segments. The vanes rotate at the same speed butin opposite directions and the rotational speed of each reachesapproximately 2,400 revolutions per minute. The vanes are typicallyconstructed of a noncorrodible metal such as stainless steel, forexample. i

The external vane 1103 is electrically connected to the ground of thecircuit. The internal vane I02 has a coil 1l07 wound about the outersurface of its shaft and coaxial with it. The coil 107 rotates with theshaft and has one of its leads connected to the shaft through anintegrated amplifier also mounted on the shaft (but now shown). Theother lead of the coil 1107 is grounded. A second coil 1100, which isfixed and nonrotating, is also mounted coaxial with the shaft of thevane 102 and adjacent to the coil 107 and is magnetically coupled to thecoil 107 to receive the signals from the vane ll02. The amplifier forthe coil 107 may be powered by an alternating signal applied through thesame or different coils which is then rectified. As will be described inreference to FIG. 9 the coil 108 is connected to a control system 200which produces a high voltage output signal to charge the ionizer nozzle109.

A cup-shaped housing 112 surrounds the backsides of the vanes I02 andI03 to not only protect the vanes from damage but also to allow anelectrostatic charge to be placed upon the. vanes during testing of thesystem. The outer edges of the housing 112 are tapered to facilitate theapplication of this electrostatic charge.

' The electrical output from the generator 106 is fed to the controlsystem 200 and is also fed to a valve control system 1113. When thevoltage output from the generator 106 exceeds a predetermined value, thevalve control 1113 feeds an output signal to a restriction valve 114between the pipe P2 and the turbine ll0l to reduce the flow ofpressurized fluid to the turbine and thereby to decrease its speed andalso to reduce the rotational speed of the generator 106. The decreasein the rotational speed of the generator 1106 consequently reduces theoutput voltage and the system is stabilized.

The generator 106 is of the type which has a permanent magnet rotor. Thefrequency of the signal produced by the generator and the number ofpoles of the generator must be double the interception frequency of theinternal and external vanes 102 and 103, respectively. For example inthe case of'a sensor, such as in the preferred embodiment, having fourvanes interception takes place eight times per complete revolution ofeach vane and therefore the generator must produce four cycles in itsalternating signal per revolution of each vane.

The system isinitially adjusted such that when the vanes areintercepting (overlying) the generator will go through an instantaneousvoltage of zero volts. This relationship is then made fixed so that thephase of the alternating signal produced by the generator is anindication of the relative position of the electrostatic vanes.

By way of example, when the internal vane 102 is exposed by the externalvane 103 to a positively charged electrostatic field within the tankthen a chopped signal is produced by the sensor 110. After eachinterception of the vanes (i.e., when the alternating generator voltageis zero) the sensor output voltage will be positive going. This signalis later compared in the phase by the circuit 200 with the generatoralternating voltage as will be explained in more detail with regard toFIG. 9 to give an indication of the polarity and magnitude of theelectrostatic field within the tank.

' Referring now more particularly to FIG. 9 the control system 200 forthe sensor comprises a pair of amplifiers 201 and 202 which have theirinputs connected to the coil 108 mounted about the shaft of the internalvane 102. The signal produced in the vane 102 is magnetically coupledthrough the coils 107 and 108 and is thereby separately transmittedthrough the amplifiers 201 and 202 to a pair of phase comparators 203and 204, respectively.

The alternating signal from the generator 106 is also connected to eachof the phase comparators 203 and 204. The phase comparators demodulatethe signals from the amplifiers 201 and 202 to determine whether thesignal is positive going or negative going with respect to thealternating signal from the generator 106. The relative phase of thesesignals from the amplifiers 201 and 202 with respect to the generatorsignal are indicative of the polarity of the electrostatic field sensedby the sensor 110.

The output from the phase comparators 203 and 204 are coupled to a servocompensation network 206. If the polarity of the field sensed by thesensor 110 is positive the phase comparator 203 will provide a signal tothe servo compensation network 206 which will then produce acorresponding output signal indicative of the positive field. If thepolarity of the field sensed by the sensor 110 is negative the phasecomparator 204 will provide asignal to the servo compensation network206 which will then produce a corresponding output signal indicative ofthe negative field.

It should be noted that if no electrostatic field is sensed by thesensor 110 the phase comparators 203 and 204 will give identical outputsignals and the servo compensation network 206 will produce no outputsignal. The servo compensation network contains circuitry to ensurestability and damping in the system and thus it does not respond to allsignals from the phase comparators 203 and 204 but only to such signalswhen they exceed a predetermined magnitude and time response.

The output signal from the servo compensation network 206 is amplifiedby an amplifier 207 and fed to a high voltage rectifying circuit 208which produces a voltage comparable in magnitude to the voltage sensedby the sensor 1 l0 and of the same polarity. The voltage from the highvoltage rectifier 208 is applied to the ionizing nozzle 109 through ahigh impedance 209 which limits the current available to the nozzle 109to an amount which is less than that which would support corona arcingto the atmosphere in the tank 100.

The power for the control system 200 is generated locally by thegenerator 106. The alternating signal from the generator is supplied toa voltage regulating and rectifying unit 210 which then provides thecircuits of the system with direct current.

Since it is vital to the safety of the oil carrier that the dischargingsystem operate without failure, numerous safeguards are provided to warnthe crew in the event that the system becomes inoperable due to amalfunction. The generator 106 is equipped with an alarm A1 which willcause a signal to be sounded on the bridge of the oil carrier in theevent that the voltage produced by the generator 106 falls below apredetermined level.

The output from the phase comparators 203 and 203 are also fed to a failsafe circuit 205 which operates an alarm A2 and which feeds a signal toa testing circuit 211. In the the event that the signals from the phasecomparators 203 and 204 exceed a predetermined level, thus indicatingthat the sensor 110 is saturated, the alarm A2 is activated by thecircuit 205 to notify the officers of the oil carrier of the situation.

The high voltage output from the high impedance 209 is also connected tothe testing circuit 211. The testing circuit 211 is connected to soundan alarm A3 if the voltage falls below the required level when thesignal from the circuit 205 indicates that there is a charge present inthe tank. The testing circuit 211 also allows the officers of the oilcarrier to periodically test the operation of the circuit 200 byapplying a high voltage field to the casing 112 surrounding the vanes102 and 103. If the circuit 200 does not respond by producing acorresponding signal of the same polarity and magnitude at the highimpedance circuit 209, the testing circuit 211 activates the alarm A3 orotherwise indicates that the system is not working properly. The alarmsAl, A2 and A3 are generally operated by a control and alarm unit 212(FIG. 7) which hydraulically connects the alarms through a pipe P3 tothe control panel for the system on the oil carriers bridge.

The system is further designed to be able to be short circuited withoutproducing arcs. For example, as was described in reference to theembodiment of FIG. 2A the ionizer nozzle is provided with a highimpedance to prevent current of magnitude sufficient to cause coronaarcing from flowing in the nozzle. The generator 106 is also designed tobe able to carry a short circuit current without arcing. I

While in the above embodiment a particular type of ionizing nozzle hasbeen described as being most efficient for the operation of this system,in other embodiments other forms of devices may be utilized for ionizingthe spray of water. Such other devices may not depend on the dielectricionization process utilized by the nozzle in the present invention. Thusin such embodiments the polarity of the high voltage signal maynecessarily be required to be the opposite of the polarity of theelectrostatic field sensed within the tank.

In some embodiments it is preferable to have a recording system toconstantly record the electrostatic field strength and polarity withinthe tank for later analysis. Information can then be correlated tocircumstances of time, period, and place of the oil carrier and othernavigation details.

The system above has been described in reference to its use in the tanksof a sea going oil carrier but it should be apparent that the system isalso suitable for use in any situation requiring the discharge of anelectrostatic field within a container. Thus, the invention may beemployed in railroad oil tanks, truck tanks, or even fixed, liquid fuelstorage tanks.

Although the output signal from the sensor of the above embodimentscontains the information regarding the electrostatic field sensed bybeing phase modulated with respect to the output from the generator, inother embodiments the sensor signal is varied in other ways to conveythe sensor information.

The terms and expressions which have been employed here are used asterms of description and not of limitation, and there is no intention inthe use of such terms and expressions, of excluding equivalents of thefeatures shown and described, or portions thereof, it being recognizedthat various modifications are possible within the scope of theinvention claimed.

. What is claimed is:

ll. A discharging system for use in neutralizing an electrostatic fieldinside a liquid fuel container comprising means for sensing themagnitude and polarity of the electrostatic field within the containerand for producing a first output signal representative of the magnitudeand polarity of the electrostatic field sensed, a first circuitresponsive to the first output signal for producing a second outputsignal when the polarity of the field sensed is positive, a secondcircuit responsive to the first output signal for producing a thirdoutput signal when the polarity of the field sensed is negative, meansresponsive to the second and the third output signals for producing ahigh voltage, electrostatic potential proportional in magnitude to theelectrostatic field by the sensor and having a predetermined polarity,and means for applying this high voltage, electrostatic potential towater particles sprayed into the container to electrostatically chargethe water particles with a polarity opposite to that sensed by thesensing means.

2. A discharging system as recited in claim ll wherein .the means forelectrostatically charging the spray of water comprises a source ofwater under pressure, an ionizer nozzle having a hollow cylindrical bodyfor receiving the pressurized water from the source, an inner corecontained in the cylindrical body, the core being helically groovedaround its periphery to impart a rotating motion tothe water, thecylindrical body having an exit opening downstream from the entrance ofthe pressurized water and the core, the exit opening being encircled byan insulated, enveloping metal cone which is connected to the means forproducing the high voltage electrostatic potential whereby the rotatingwater expelled through the exit opening forms a hollow cone within theenveloping insulated metal cone and having a wall thickness whichdiminishes outwardly to the point where the wall of water finally breaksinto particles charged with a polarity opposite to that of the highvoltage electrostatic potential to which the metal cone is connected,the broken away particles of charged water thereafter being carried bytheir own momentum into the interior of the container to neutralize theelectrostatically charged atmosphere therein.

3. A discharging system as recited in claim 2 wherein the envelopingmetal cone comprises an insulating and mechanically resistant substrate,a plurality of conductor rings deposited on the substrate and having ahigh specific resistance, and a plurality of high value resistorsinterconnecting the rings and encapsulated within the cone, theresistance of the rings and of the resistors being great enough toprevent current from flowing in the cone which would otherwise besufficient in magnitude to sustain corona arcing from the cone, andmeans for connecting the rings through the resistors to the highvoltage, electrostatic potential.

4. A discharging system as recited in claim ll wherein the sensing meanscomprises a first and a second vane, means for coaxially and rotatablymounting the first and the second vanes inside the container, means forrotating the vanes relative to each other at a predetermined speed, eachof the first and the second vanes having a predetermined number ofspaced apart segments, means for shielding the first and the secondvanes such that the first vane is continuously exposed to theelectrostatic field within the container and the second vane isperiodically exposed by the spaces between the segments of the firstvane as the first and the second vanes are rotated relative to eachother, and means connected to the first and the second vanes foramplifying the voltage difference between the vanes induced by theelectrostatic field within the container and for producing the firstoutput signal representative of the magnitude and the polarity of theelectrostatic field within the container.

5. A discharging system as recited in claim 4 wherein the means forrotating the first and the second vanes counterrotates the first and thesecond vanes and wherein each of the first and the second vanes has four45 segments.

6. A discharging system as recited in claim 4 wherein the amplifyingmeans connected to the first and the second vanes includes an integratedamplifier connected to the second vane, a first coil having one leadconnected to the output of the integrated amplifier, means for mountingthe integrated amplifier and the first coil for rotation with the secondvane, a second coil, means for mounting the second coil adjacent thefirst coil such that the first and the second coils are magneticallycoupled, means connected to the second coil for amplifying the signalmagnetically induced in the second coil by the first coil and means forgrounding the first vane and the other lead of the first coil.

7. A discharging system as recited in claim a further comprising meansfor generating an alternating current reference signal whose frequencyis synchronized with the rotation of the first and the second vanes insuch a manner that the alternating signal has substantially zero voltagepotential at the moments in time when segments of the second vane areshielded from the electrostatic field within the container by thesegments of the first vane, and wherein the first and the secondcircuits both include means responsive to the reference signal forcomparing the phase of the first output signal with the phase of thereference signal.

a. A discharging system as recited in claim 4 wherein the means forshielding the-first and the second vanes includes an electrode and meansfor applying a high voltage to the electrode to impress a testelectrostatic charge on the first and the second vanes.

9. A discharging system as recited in claim 4 further comprising meansfor cleaning the first and the second vanes with high pressure streamsof water and compressed air 10. A discharging system as recited in claim1 wherein the system is powered by a hydraulic turbine mounted in theimmediate vicinity of the liquid fuel container.

11. A system for neutralizing an electrostatic charge existing inside atank designed to contain liquid fuel comprising means for sensing theexistence, magnitude and polarity of the electrostatic charge presentinside the tank and for generating a first signal representative of themagnitude and polarity of the electrostatic charge sensed, means foramplifying the first signal means for generating a reference signal,means for comparing the phase of the amplified first signal with that ofthe reference signal to determine the polarity of electrostatic charge.

1. A discharging system for use in neutralizing an electrostatic field inside a liquid fuel container comprising means for sensing the magnitude and polarity of the electrostatic field within the container and for producing a first output signal representative of the magnitude and polarity of the electrostatic field sensed, a first circuit responsive to the first output signal for producing a second output signal when the polarity of the field sensed is positive, a second circuit responsive to the first output signal for producing a third output signal when the polarity of the field sensed is negative, means responsive to the second and the third output signals for producing a high voltage, electrostatic potential proportional in magnitude to the electrostatic field by the sensor and having a predetermined polarity, and means for applying this high voltage, electrostatic potential to water particles sprayed into the container to electrostatically charge the water particles with a polarity opposite to that sensed by the sensing means.
 2. A discharging system as recited in claim 1 wherein the means for electrostatically charging the spray of water comprises a source of water under pressure, an ionizer nozzle having a hollow cylindrical body for receiving the pressurized water from the source, an inner core contained in the cylindrical body, the core being helically grooved around its periphery to impart a rotaTing motion to the water, the cylindrical body having an exit opening downstream from the entrance of the pressurized water and the core, the exit opening being encircled by an insulated, enveloping metal cone which is connected to the means for producing the high voltage electrostatic potential whereby the rotating water expelled through the exit opening forms a hollow cone within the enveloping insulated metal cone and having a wall thickness which diminishes outwardly to the point where the wall of water finally breaks into particles charged with a polarity opposite to that of the high voltage electrostatic potential to which the metal cone is connected, the broken away particles of charged water thereafter being carried by their own momentum into the interior of the container to neutralize the electrostatically charged atmosphere therein.
 3. A discharging system as recited in claim 2 wherein the enveloping metal cone comprises an insulating and mechanically resistant substrate, a plurality of conductor rings deposited on the substrate and having a high specific resistance, and a plurality of high value resistors interconnecting the rings and encapsulated within the cone, the resistance of the rings and of the resistors being great enough to prevent current from flowing in the cone which would otherwise be sufficient in magnitude to sustain corona arcing from the cone, and means for connecting the rings through the resistors to the high voltage, electrostatic potential.
 4. A discharging system as recited in claim 1 wherein the sensing means comprises a first and a second vane, means for coaxially and rotatably mounting the first and the second vanes inside the container, means for rotating the vanes relative to each other at a predetermined speed, each of the first and the second vanes having a predetermined number of spaced apart segments, means for shielding the first and the second vanes such that the first vane is continuously exposed to the electrostatic field within the container and the second vane is periodically exposed by the spaces between the segments of the first vane as the first and the second vanes are rotated relative to each other, and means connected to the first and the second vanes for amplifying the voltage difference between the vanes induced by the electrostatic field within the container and for producing the first output signal representative of the magnitude and the polarity of the electrostatic field within the container.
 5. A discharging system as recited in claim 4 wherein the means for rotating the first and the second vanes counterrotates the first and the second vanes and wherein each of the first and the second vanes has four 45* segments.
 6. A discharging system as recited in claim 4 wherein the amplifying means connected to the first and the second vanes includes an integrated amplifier connected to the second vane, a first coil having one lead connected to the output of the integrated amplifier, means for mounting the integrated amplifier and the first coil for rotation with the second vane, a second coil, means for mounting the second coil adjacent the first coil such that the first and the second coils are magnetically coupled, means connected to the second coil for amplifying the signal magnetically induced in the second coil by the first coil and means for grounding the first vane and the other lead of the first coil.
 7. A discharging system as recited in claim 4 further comprising means for generating an alternating current reference signal whose frequency is synchronized with the rotation of the first and the second vanes in such a manner that the alternating signal has substantially zero voltage potential at the moments in time when segments of the second vane are shielded from the electrostatic field within the container by the segments of the first vane, and wherein the first and the second circuits both include means responsive to the reference signal for comparing the phase of the first output signaL with the phase of the reference signal.
 8. A discharging system as recited in claim 4 wherein the means for shielding the first and the second vanes includes an electrode and means for applying a high voltage to the electrode to impress a test electrostatic charge on the first and the second vanes.
 9. A discharging system as recited in claim 4 further comprising means for cleaning the first and the second vanes with high pressure streams of water and compressed air.
 10. A discharging system as recited in claim 1 wherein the system is powered by a hydraulic turbine mounted in the immediate vicinity of the liquid fuel container.
 11. A system for neutralizing an electrostatic charge existing inside a tank designed to contain liquid fuel comprising means for sensing the existence, magnitude and polarity of the electrostatic charge present inside the tank and for generating a first signal representative of the magnitude and polarity of the electrostatic charge sensed, means for amplifying the first signal, means for generating a reference signal, means for comparing the phase of the amplified first signal with that of the reference signal to determine the polarity of the electrostatic charge existing in the tank and for generating a resulting D.C. voltage proportional in magnitude to the tank''s charge and with the same polarity as the tank''s charge, a high-pressure ionized water sprayer for spraying water into the interior of the tank, means for applying the D.C. voltage to the water sprayer so that the water spray will carry a charge of polarity opposite to that of the electrostatic charge existing in the atmosphere inside the tank and thereby neutralize the electrostatic charge. 